Both sides of the wind-up clock are transparent, meaning that the workings of the clock are completely visible. This brilliant discovery kit is designed to give children aged from 5 to 15 an understanding of how a clock actually works. Children will be able to see why the different cogs and springs rotate and how they cause the pendulum to swing, turn the hands of the clock and make the bell chime as too! Once fully wound the Clock Kit should run for around 6 hours. Clock face approx.19.5cm